The usual positioning system is for the terminal to determine its position thanks to GPS signal by measuring signals emitted by the Global Positioning System satellite network, then to report this information to the hub via any communication network (cellular, satellite . . . ).
Other systems exist, which use an hybrid approach, where the terminal measures some properties, e.g. the delay in the reception of pilot signals from two different satellites, and sends the results to the Network operating center (NOC) via a telecom network, e.g. satellite itself; in a second phase the Network operating center uses these measurements to calculate the terminal position.
Note that all methods described above require an active “collaboration” by the terminal, and rely on the exactness of the information provided by the terminal to the hub. The drawback in this scenario is that the terminal may report a false position or report false information so that the network operating center calculates a false position, and the network operating center has no way to certify the truth of the information. Within an application involving payments, or tracking dangerous goods, it is possible that “pirate” terminals are developed that intentionally report a false position so as to avoid or reduce payments; these pirate terminals would be undetectable by the network operating center.
Besides, in satellite environment, sophisticated methods exist to perform triangulation and locate, within ˜100 km, the position of a source of interference or jamming. These methods are very expensive, as they require sophisticated material as well as access to different satellites in order to perform triangulation. Also, they are based on a long period of observation of the signal. They cannot be used for single signal or in the framework of a consumer service.
The document FR no 1154663 proposes a solution based on measures of relative amplitudes. That invention requires the use of a multi-beam satellite, and the precision highly depends on the geometry of the beams operating on a same frequency band. This requirement restricts its applicability to few satellite systems in the world. Also, the problem of “impersonation”, i.e. a terminal pretending to be another one, was not addressed.